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Frequency-modulated (FM) signals are widely used in sensing, measurement, and signal detection due to their strong anti-interference and easy transmission characteristics. Although the high-precision measurement methods for static signals are quite complete, the high-precision measurement methods for dynamic FM signals still need to be studied, and the measurement accuracy in the high-sampling system still has room for improvement. Traditionally, the equal-precision measurement method is widely applied in most scenarios. However, its accuracy is limited by the quantization error of ±1 word and the sampling gate time, making it difficult to improve the frequency measurement accuracy while ensuring a high sampling rate at the same time. In this paper, a high-precision feedback frequency measurement system with the capability to eliminate the quantization error of ±1 word is proposed. The proposed system consists of two stages, the rough measurement stage based on the equal-precision measurement method and the precise measurement stage based on the negative feedback tracking architecture using the phase–frequency detector (PFD) and direct digital synthesizer (DDS). The effectiveness and feasibility of the system are verified by both simulation and experiment. At the sampling rate of 2 kHz, the frequency measurement accuracy is improved by more than 30 dB.

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Diagnosis of the dynamic response of an asphalt pavement structure coupled with involving inherent anisotropic properties of pavement materials serves as a vital tool for pavement analysis and design platforms. The mechanical response of asphalt pavement is strongly influenced by the random anisotropic properties (simplified as transversely isotropic properties in this study) because of the shape, distribution, orientation, degree of compaction, void structure, and so forth, of the granular materials in asphalt pavements. This study aims to introduce a computational framework by generating a three-dimensional finite element-based program to analyze the influence of thermo-viscoelasticity of the asphalt layer and transverse isotropy of the base courses and its randomness on asphalt pavements under the effect of moving vehicle loading. The accuracy and efficiency of the developed numerical program were verified by comparing our results with previous studies. Concurrently, the influences of random field conditions, transversely isotropic properties, and the temperature field were involved in assessing their action on the fatigue life prediction of pavement. It was concluded that the fatigue life of the asphalt pavement model, considering the transverse isotropy of the material, random field, and temperature field, was reduced by 48.1%, which would mislead the state assessment of asphalt pavements. Therefore, during asphalt pavement design and its viscoelastic response analysis, it is recommended to consider the influence of the random modulus, temperature fields, and transversely isotropic properties on the structural assessments.